Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS6071624 A
Publication typeGrant
Application numberUS 09/160,495
Publication date6 Jun 2000
Filing date24 Sep 1998
Priority date22 May 1996
Fee statusLapsed
Also published asCA2252878A1, CA2252878C, CN1100818C, CN1219182A, DE69709728D1, EP0900250A1, EP0900250B1, EP0900250B2, US5882798, WO1997044379A1
Publication number09160495, 160495, US 6071624 A, US 6071624A, US-A-6071624, US6071624 A, US6071624A
InventorsFrank P. Battito, Douglas R. Holcomb, Michael A. Hubbard, James A. McCaulley
Original AssigneeHoechst Trespaphan Gmbh
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Lithium and potassium copolysilicate barrier coatings
US 6071624 A
Abstract
A method and novel barrier coating solutions are provided for imparting improved vapor, gas or aroma permeability characteristics to a coated polymeric substrate. The method and solutions employ a lithium-potassium copolysilicate of the formula (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y. For the method, y is between 1 and 10, if x is less than 1; or y is greater than 4.6, if x is 1. For the novel coating solutions, y is greater than 4.6 if x is less than 1; or x is greater than 0.5 if y is between 1 and 10.
Images(1)
Previous page
Next page
Claims(14)
What is claimed is:
1. An aqueous barrier coating solution for polymeric substrates comprising a lithium-potassium copolysilicate of the formula (M.sub.2 O)(SiO.sub.2).sub.y, wherein M.sub.2 O is (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x and wherein x ranges from 0.5 to less than 1, and y ranges from 1 to about 10, said solution comprising about up to 15% total solids content.
2. The coating solution according to claim 1 wherein x is between 0.5 and 1 and y is between 4.6 and 10.
3. The coating solution according to claim 1 additionally comprising a suitable surfactant.
4. The coating solution according to claim 1, wherein the surfactant is non-ionic.
5. The coating solution according to claim 4 wherein the surfactant is selected from the group consisting of acetylenic glycols and alkyl ethoxylates.
6. The coating solution according to claim 1 wherein said coating is a barrier to a vapor, a gas or an aroma.
7. The aqueous solution according to claim 1, said solution comprising about 12% total solids content.
8. The aqueous solution according to claim 1, said solution comprising about 10% total solids content.
9. The aqueous solution according to claim 1, said solution comprising about 2% total solids content.
10. The aqueous solution according to claim 1, said solution comprising about 85% water content.
11. The aqueous solution according to claim 1, said solution additionally comprising about 1 wt. % priming solution.
12. The aqueous solution according to claim 11, wherein said priming solution is poly(p-hydroxystyrene).
13. The aqueous solution according to claim 1, wherein said solution is colorless and transparent.
14. An aqueous barrier coating solution for polymeric substrates comprising a lithium-potassium copolysilicate of the formula (M.sub.2 O)(SiO.sub.2).sub.y, wherein M.sub.2 O is (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x and wherein x is about 0.83 and y is about 3.91, said solution comprising up to about 15% total solids content.
Description
DETAILED DESCRIPTION OF THE INVENTION

The present invention overcomes the deficiencies in prior art vapor barrier coatings. This invention includes a method for providing improved vapor, gas, and/or aroma barrier properties at high relative humidities to polymeric substrates using coating solutions containing a lithium-potassium co-polysilicate. The invention also provides novel coating solutions for the substrate as well as improved coated articles. The coating solutions used in the present method provide excellent vapor, gas and aroma barrier characteristics at high relative humidity in comparison with pure potassium polysilicates, and exhibit markedly reduced rates of efflorescence in comparison with pure lithium polysilicates.

I. Definitions

The term "vapor" implies a liquid at partial pressure, such as water vapor. The term "gas" includes oxygen, nitrogen, carbon dioxide and others. "Aroma" includes those materials which bear a fragrance, for example, menthol and others. For simplicity, as used herein, the term "vapor barrier" can be interpreted to mean a barrier to gases and aromas as well as traditionally defined vapors.

Similarly as used herein, the term "solution" is interpreted to include colloidal dispersions and suspensions. By "colloidal dispersion or suspension" is meant any dispersion or suspension of particles in liquid, the particles being of a size greater than molecular scale that do not settle out. Generally the particle size in a suspension or dispersion of this invention are from about 10 to about 50,000 Angstroms. "Coating solution" as used herein is meant a liquid containing dissolved or suspended solids that do not settle out and which is used to apply said solids to a substrate.

II. The Invention

The method of the invention specifically involves coating a polymeric substrate with a barrier coating solution containing a lithium and potassium copolysilicate. The coating solution contains a copolysilicate, i.e., a mixture of two different alkali metal polysilicates. More specifically, the coating solutions result from a mixture of lithium and potassium polysilicates. These coating solutions are characterized by copolysilicate of the general formula (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y, in which the mole fraction of Li.sub.2 O is x and the molar ratio of SiO.sub.2 to M.sub.2 O is y. In the coating solutions useful in the method of the present invention, the co-polysilicate is one in which y is between 1 and 10, if x is less than 1, or y is greater than 4.6 if x is 1.

Certain novel coating solutions for use in the above-described method are provided by the formula above, in which y is greater than 4.6 if x is less than 1; or x is greater than 0.5 if y is between 1 and 10. More preferably, a novel coating solution of this invention is characterized by a value of x between 0.5 and 1 and a value of y between4.6 and 10.

Coating solutions useful in the method, as well as the novel coating solutions of this invention, can also contain a suitable surfactant to reduce surface tension. Surfactants can be anionic, cationic and non-ionic, and many surfactants of each type are available commercially. Preferably, the surfactant useful in the methods and solutions of this invention is nonionic. A suitable surfactant for inclusion in these compositions possesses a critical micelle concentration sufficiently low to ensure a dried coating uncompromised by residual surfactant. Most preferably, the surfactant is selected from the group consisting of acetylenic glycols (e.g., such as those provided commercially by Air Products) and alkyl ethoxylates (such as those provided commercially by Hoechst Celanese and many others). The amount of surfactant added to the coating solution or composition will depend on the particular surfactant selected, but should be the minimum amount of surfactant that is necessary to achieve wetting of the polymer substrate while not compromising the performance of the dried coating. For example, typical surfactant amounts can be less than or equal to about 0.1% by weight of an acetylenic glycol or an alkyl ethoxylate.

A typical coating solution according to this invention is preferably colorless and transparent. A coating solution of the invention may be prepared from commercially available lithium polysilicate and potassium polysilicate solutions. For example, a commercially available colloidal suspension of lithium polysilicate may be blended with a commercially available potassium polysilicate colloidal suspension to make the coatings of the present invention. It should be noted that one can prepare the coating solutions of the invention by using the "parent" products which are used to produce the commercially available polysilicates. However, such preparation is well-known and unnecessary in view of the commercial availability of the lithium and potassium polysilicate solutions.

As illustrated in Example 1 below, one exemplary commercially available product bearing the trademark Inobond is an aqueous colloidal suspension of lithium polysilicate which contains 24.5% by weight silicon dioxide and 3.0% by weight lithium oxide. Another useful product bears the trademark K-4009 (van Baerle & Cie AG) and is an aqueous colloidal suspension containing 26.8% by weight silicon dioxide and 13% by weight potassium oxide. Such components are then mixed with water to produce a desired solids content.

The molar ratio, y, of SiO.sub.2 :M.sub.2 O of the dried coatings may be determined by the molar ratios of SiO.sub.2 :Li.sub.2 O and SiO.sub.2 :K.sub.2 O in the starting alkali metal polysilicates. One may, however, desire to modify the overall SiO.sub.2 :M.sub.2 O mole ratio in the copolysilicate coating. This may be accomplished by the addition of aqueous suspensions of colloidal silica to the coating solution. As described in Example 4, below, one exemplary commercially available product bearing the trademark Ludox Chemicals) is an aqueous colloidal suspension of silicon dioxide which contains 30% by weight solids. Such colloidal dispersions are available under a variety of trademarks including Ludox Chemicals) and Klebosol

While a typical useful solids content for coating solutions of this invention is up to about 25% by weight of solids, the desired solids content depends entirely on the coating method used, and may be readily adjusted by techniques well known to the art to achieve a desired coating thickness of the dry coating on the selected substrate. For example, coating on a thin film or sheet are desirably between about 200 to about 500 nm of dry coating, and more preferably about 300 nm. Coatings on rigid or semi-rigid containers are desirably from about 100 to about 1000 nm of dry coating. Such an adjustment is well within the skill of the art [see, e.g., Canadian Patent No. 993,738].

The vapor barrier coating mixtures are then subjected to a period of stirring and, optionally, filtration. Optionally, a surfactant may be added at this stage to reduce the surface tension of the coating solution. For example, the commercially available Genapol surfactant (Hoechst Celanese) or other surfactants represented by trademarks such as Genapol added at this stage. The vapor barrier coating solution is thus ready to be applied to a polymeric surface or substrate.

The lithium-potassium copolysilicate coatings of the invention can be used on a variety of polymeric surfaces and articles to improve (i.e., reduce) the permeability of the products to vapors, such as oxygen, carbon dioxide, nitrogen and others. Typical organic aromas and vapors include, but are not limited to, d-limonene, cinnamaldehyde, vanillin, menthol, gasoline, perfume fragrances, and the like. These coatings are particularly advantageous where the polymers used to prepare the article or substrate do not provide sufficient vapor, gas, or aroma impermeability for the desired application.

Suitable substrates to be coated with the above-described coating solutions include substrates formed of polymers including polyesters, such as poly(ethylene terephthalate) (PET); polyolefins, particularly polypropylene, polystyrene, polyethylene and cycloolefins (COC), such as a copolymer of ethylene and norbornene [U.S. Pat. No. 5,087,677]; and polyamides, such as nylon. The articles coated by these coatings include, without limitation, polymeric films and sheets, rigid and semi-rigid containers, and other surfaces. Especially preferred articles for coating according to this invention include polypropylene films, PET films, nylon films, films used in covering food products (e.g., meats, poultry, etc.), beverage bottles, plastic containers, jars, blisterpacks and lidstocks, made of the foregoing polymers.

The polymeric articles to be coated by the compositions of the invention may be previously untreated. Optionally, the polymeric article, such as a film or bottle, may be first plasma treated to improve wetting and adhesion by the barrier coating as described in the following Example 1. Alternatively, the polymeric article may be corona-treated by the industry-wide corona discharge treatment method. In instances where corona-treatment of the polymer does not cause suitable wetting of the coating on the polymer, a suitable primer may be first applied to the polymeric article. For example, in the case of polypropylene, a primer solution of poly(vinyl alcohol) or poly(hydroxystyrene) may be used to improve wetting of the barrier coating solutions on the polymer.

The polymer may also have been flame treated, or chemically etched and oxidized prior to the application of the coating solution of this invention.

The substrate may be a film that contains on at least one side a heat seal layer. Such heat seal layers may be made of an ethylene-propylene copolymer or ethylene-propylene-butylene terpolymer. Thus, the coating solution is applied on the surface of the heat seal layer. Alternatively, where a film contains one side coated with the heat seal layer, the coating solution of the present invention can be applied to the surface of the film opposite the surface coated with the heat seal layer. The polymeric substrate or article may also comprise a protective topcoat layer. The coatings of this invention may be applied over the topcoat layer.

The coatings of this invention may be applied to the selected polymeric surface or article by conventional coating techniques known to those of skill in the art. These techniques include, without limitation, roll coating, spray coating, and dip coating techniques. Roll coating techniques include, but are not limited to, rod, reverse roll, forward roll, air knife, knife over roll, blade, gravure and slot die coating methods. General descriptions of these types of coating methods may be found in texts, such as Modern Coating and Drying Techniques, (E. Cohen and E. Gutoff, eds; VCH Publishers) New York (1992) and Web Processing and Converting Technology and Equipment, (D. Satas, ed; Van Nostrand Reinhold) New York (1984). Three dimensional articles may be coated by spray coating or dip coating. The method of application is not a limitation on the present invention, but may be selected from among these and other well-known methods by the person of skill in the art.

After coating, the coated product must be dried at a selected temperature of room temperature or greater than room temperature. The selection of the drying temperature depends on the desired time for drying; that is, accelerated drying times may be achieved at elevated temperatures which would not be necessary if a longer time period for drying was acceptable. One of skill in the art can readily adjust the oven temperature and drying time as desired. The performance of the dried vapor barrier coating is insensitive to the drying temperature over the range 25-200 significant advantage of the present coatings and method is that low temperature (<100 requirements of biaxially oriented polypropylene (BOPP) film processing.

The compositions and methods of this invention are further illustrated by the following examples, which are not intended to limit the scope of this invention.

EXAMPLE 1 Variation of Lithium Oxide Mole Fraction in Copolysilicate Coatings on Biaxially Oriented Pet Film

A. Preparation of Coating Solutions

A series of seven lithium-potassium copolysilicate barrier coating solutions of the invention were prepared, as indicated in Table 1. The compositions of these polysilicate coatings of the invention are expressed as the mole fraction, x, of Li.sub.2 O in the copolysilicate (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y, with values of x ranging from 0 to 1. With continuous stirring, Inobond polysilicate solution (van Baerle & Cie AG) having 3.0% w/w Li.sub.2 O and 24.5% w/w SiO.sub.2, was mixed with water. K-4009 potassium polysilicate solution (van Baerle & Cie) having 13.0% w/w K.sub.2 O and 26.85% w/w SiO.sub.2 was added to the lithium polysilicate solution. Genapol 26-L-60N nonionic surfactant (Hoechst Celanese), as a 1% by weight solution in water, was then added to improve wetting of the poly(ethylene terephthalate) (PET) substrates. Each coating mixture in Table 1 was stirred overnight then filtered through diatomaceous earth. The resulting coating solutions had 15% total solids and 0.01% surfactant. The SiO.sub.2 :M.sub.2 O mole ratio, y, ranged from 3.24 at x=0 to 4.05 at x=1

              TABLE 1______________________________________Recipes for Preparing a Series of Lithium-PotassiumCopolysilicates for Barrier Coatings                        Mass of Mass of   Mass    Mass 1.0%    Mole  SiO.sub.2 :Solu- Inobond            of      of   Genapol                                 Fraction                                      M.sub.2 Otion  Li 2043   K-4009  H.sub.2 O                        26-L-60N                                x of  moleNo.   (g)       (g)     (g)  (g)     Li.sub.2 O                                      ratio______________________________________1     0         75.3    122.7                        2.0     0.00  3.242     17.7      63.0    117.3                        2.0     0.17  3.383     35.7      50.6    111.7                        2.0     0.34  3.514     53.1      38.8    106.1                        2.0     0.50  3.645     70.6      26.5    100.9                        2.0     0.66  3.776     89.6      13.4    95.0 2.0     0.83  3.917     109.1     0       88.9 2.0     1.00  4.05______________________________________

B. Preparation of Coated Films

Four inch circles were cut from PET film (Hoechst Diafoil, Hostaphan 2400, 0.5 mil thick) with a scalpel. Any dust on the film was blown off with a jet of clean, filtered air. The samples were then plasma treated to improve wetting by copolysilicate coating solutions and adhesion of dried copolysilicate coatings. Plasma treatment was performed using a Plasma Preen microwave reactor operated at 50% power with 2 Torr of oxygen. The treatment duration was 5 s. Approximately 10 g of coating solution was dispensed on the PET film before spinning at 2000 rpm for 10 s. The coated films were dried in an oven maintained at 50

Several coated film samples were prepared with each coating solution described in Table 1. Separate samples were selected for accelerated aging/haze measurements and oxygen transmission rate (OTR) measurements as a function of relative humidity.

C. Measurement of Haze Formation

Optical haze was measured with a spectrophotometer (MacBeth Color-Eye 7000) conforming to ASTM D 1003-61. Samples were characterized shortly after spin-coating and then placed in an environmental chamber (Tenney T H Jr.) maintained at 80 periodically removed from the chamber for haze measurement over a period of two weeks.

The initial linear rate of haze formation by efflorescence is calculated by least-squares fit to a plot of % haze vs. time. At longer times the % haze reaches a plateau, with the plateau value proportional to the lithium content of the copolysilicate coating. FIG. 1 depicts the dependence of the initial rate of haze development on coating composition. The hazing rate increases linearly with increasing lithium content.

D. Measurement of Oxygen Transmission Rates

The barrier performance of the coated film samples was assessed by measurement of the OTR. OTR measurements were performed using a Mocon Oxtran 2000 instrument. Table 2 presents OTR values at 30 units: cm.sup.3 /[m.sup.2 atm day]) vs. relative humidity for a series of (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y copolysilicate barrier coatings on 0.5 mil PET film.

              TABLE 2______________________________________Oxygen Transmission Rates (cm.sup.3 /[m.sup.2 day atm]) ofLithium-Potassium Copolysilicate Barrier Coatings on 0.5 milthick PET film vs. Composition and Relative HumidityMoleFraction   Relative Humidityx of Li.sub.2 O   Dry      40%     60%   70%   80%   90%______________________________________0.00    13.1     9.5     75.4  115.8 132.1 131.60.17    4.5      4.5     5.9   33.1  87.2  128.40.34    3.1      3.1     3.0   1.8   42.0  101.10.50    3.7      3.2     3.1   2.7   14.3  17.70.66    7.7      4.9     4.2   3.0   3.1   15.50.83    15.5     6.5     5.8   5.4   2.2   12.71.00    14.8     8.8     7.9   7.5   5.4   13.5______________________________________

Copolysilicate coatings containing little lithium (x<0.34) suffer severe loss of barrier performance at high humidity. Copolysilicate coatings, where 0.5<x<1, provide good barrier performance at high humidity on PET film while, as shown in FIG. 1, having significantly reduced susceptibility to efflorescence, as compared to a lithium polysilicate coating.

EXAMPLE 2 Variation of the Lithium Oxide Mole Fraction of Copolysilicate Coatings on Biaxially Oriented Pet Film

A. Preparation of Solutions

A series of three lithium-potassium copolysilicate barrier coating solutions was prepared using the following recipe and quantities listed in Table 3. As in Example 1, the value x refers to the mole fraction x of Li.sub.2 O in the copolysilicate (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y. With continuous stirring, Inobond mixed with distilled water. K-4009 potassium polysilicate solution was added with stirring to the lithium polysilicate solution. The resulting coating solutions had 10% total solids. The SiO.sub.2 :M.sub.2 O mole ratio, y, ranged from 3.51 at x=0.33 to 3.78 at x=0.67. Analogous solutions containing 10% solids of the individual alkali metal polysilicates were prepared as comparative samples.

B. Preparation of Coated Film

Four inch circles were cut from biaxially oriented PET film (Hoechst Diafoil, Hostaphan the film was blown off with a jet of clean, filtered air. The samples were then plasma treated with a Plasma Preen microwave reactor operated at 50% power and 2 Torr of oxygen. The treatment time was 5 s. Approximately 10.0 g of coating solution was dispensed onto the polymer film. A spreading spin cycle of 2 s at 350 rpm was followed by a spin cycle of 10 s at 2000 rpm. The coated films were dried in an oven maintained at 50 for about 30 s. Several coated film samples were prepared with each coating solution described in Table 3.

              TABLE 3______________________________________Recipes for the Preparation of Lithium-PotassiumCopolysilicate Barrier Coatings  Mole     SiO.sub.2 :M.sub.2 O                     Mass of Mass of                                   Mass ofSolution  Fraction Mole      Inobond                              K-4009                                   WaterNo.    x of Li.sub.2 O           Ratio     Li 2043 (g)                             (g)   (g)______________________________________1      0.00     3.24      --      125.5 374.52      0.33     3.51      57.8    85.6  356.63      0.50     3.64      88.4    64.5  347.14      0.67     3.78      119.6   43.0  337.55      1.00     4.05      181.8   --    318.2______________________________________

C. Measurement of Oxygen Transmission Rate

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument. Table 4 presents the oxygen transmission rate results for copolysilicate coated PET film as a function of relative humidity. As a point of reference, uncoated Hostaphan possesses an oxygen transmission rate of approximately 170 cm.sup.3 /[m.sup.2 day atm] when tested at 30 The OTR reduction for this example is significantly better than the data in Example 1.

              TABLE 4______________________________________Oxygen Transmission Rates of Lithium-PotassiumCopolysilicate Barrier Coatings on 0.5 mil thickPET film vs. Composition and Relative Humidity                  O.sub.2 Transmission RateMole Fraction       Relative   (cm.sup.3 /[m.sup.2 day atm]x of Li.sub.2 O       Humidity (%)                  at 30______________________________________0.00        0          3.721.00        0          0.410.00        90         1261.00        90         2.750.00        60         381.00        30         0.430.33        0          1.290.67        0          0.110.50        45         1.040.50        45         0.02______________________________________
EXAMPLE 3 Variation of Lithium Oxide Mole Fraction in Copolysilicate Coatings on Biaxially Oriented Polypropylene Film

A. Preparation of Solutions

A series of three lithium-potassium copolysilicate barrier coating solutions were prepared as described in Example 2. Analogous solutions containing 10% solids of the individual alkali metal polysilicates were prepared as comparative samples. Additionally a priming solution consisting of poly(p-hydroxystyrene) in aqueous base was prepared by adding in order, with stirring, 4.19 g of lithium hydroxide monohydrate and 1.00 g polymer grade poly(p-hydroxystyrene) in sufficient distilled water to make 100.0 ml of solution. The resulting solution contained 1% by weight poly(p-hydroxystyrene) in 0.1 N aqueous lithium hydroxide.

B. Preparation of Coated Film

Four inch circles were cut from biaxially oriented polypropylene film (Trespaphan film was blown off with a jet of clean, filtered air. The samples were then plasma treated with a Plasma Preen microwave reactor operated at 50% power and 2 Torr of oxygen. The treatment time was 5 s. Approximately 10 g of poly(p-hydroxystyrene) primer solution was dispensed onto the polymer film. A spreading spin cycle of 2 s at 350 rpm was followed by a spin cycle of 10 s at 2000 rpm. The primed films were dried in an oven maintained at 50 g of lithium-potassium copolysilicate barrier coating solution was dispensed onto the primed polymer film. A spreading spin cycle of 2 s at 350 rpm was followed by a spin cycle of 10 s at 2000 rpm. The coated films were dried in an oven maintained at 50

Several coated film samples were prepared with each coating solution described in Table 3. As comparative samples, films were also prepared in which the copolysilicate coating step was omitted.

C. Measurement of Oxygen Transmission Rates

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument. Table 5 presents the oxygen transmission rate results for copolysilicate barrier coated biaxially oriented polypropylene film (1.2 mil thick) as a function of relative humidity. As a point of reference, uncoated FND 30 grade polypropylene possesses an oxygen transmission rate of approximately 1700 cm.sup.3 /[m.sup.2 day atm] when tested at 30 obtained for primed but uncoated film as shown in Table 5.

              TABLE 5______________________________________Oxygen Transmission Rates of Lithium-PotassiumCopolysilicate Barrier Coatings on 1.2 mil thickBOPP film vs. Composition and Relative Humidity                   O.sub.2 Transmission RateMole Fraction        Relative   (cm.sup.3 /[m.sup.2 day atm]x of Li.sub.2 O        Humidity (%)                   at 30______________________________________0.00          0          4011.00         90          440.00         90         15971.00         30          7110.00         60          1571.00          0         12170.67          0         11900.33         90          4000.50         45          45Primed film with         0         1661no copolysilicatecoating______________________________________
EXAMPLE 4 Variation of Silica:Metal Oxide Mole Ratio in Copolysilicate Coatings Containing Equimolar Amounts of Lithium and Potassium Oxides

Example 1 demonstrates that the rate of haze formation by efflorescence in lithium polysilicate barrier coatings can be reduced by adding potassium silicate. Addition of potassium silicate, however, compromises the excellent oxygen barrier performance of lithium silicate coatings at high humidity. A balance of low efflorescence rate and satisfactory barrier performance at high humidity is achieved with approximately equimolar lithium-potassium copolysilicate blends.

A copolysilicate barrier coating with a lithium:potassium mole ratio of one produced from K-4009 (SiO.sub.2 :K.sub.2 O=3.24) and Li 2043 (SiO.sub.2 :Li.sub.2 O=4.06), has a SiO.sub.2 :M.sub.2 O mole ratio, y, of 3.64. In this experiment, y was increased by either: (1) using a potassium polysilicate solution with a higher SiO.sub.2 :K.sub.2 O mole ratio or (2) adding colloidal silica. The first approach permits y of the present copolysilicate coatings to be increased from 3.64 to 4 The upper limit of y is dictated by the SiO.sub.2 :K.sub.2 O mole ratio of commercially available potassium polysilicate coating solutions. The second approach, adding colloidal SiO.sub.2, permits solutions of even higher y value to be prepared.

A. Preparation of Coating Solutions

In this example, the source of lithium polysilicate was Inobond 2043. The source of potassium polysilicate was either K-4009 or KASIL #1 potassium polysilicate solution (PQ Corporation) having 8.30% w/w K.sub.2 O and 20.8% W/W SiO.sub.2. The colloidal silica source was chosen from the list of Ludox Chemicals) described in Table 6. Dupont's Ludox encapsulated in Al.sub.2 O.sub.3. Equivalent products marketed under the tradename Klebasol

              TABLE 6______________________________________Description of Dupont Specialty ChemicalsLudox Colloidal Silica                 ParticleGrade       Counterion  % Solids Size (nm)______________________________________Ludox        sodium      40.0     12Ludox        ammonium    30.0     22Ludox        sodium      45.0     22       (Al.sub.2 O.sub.3)______________________________________

A series of lithium-potassium copolysilicate barrier coating solutions with a Li.sub.2 O mole fraction of x=0.5 and differing SiO.sub.2 :M.sub.2 O mole ratios, y, was prepared according to the amounts listed in Table 7. In one experiment a potassium silicate solution, KASIL SiO.sub.2 :K.sub.2 O mole ratio of 4 was used. With continuous stirring, distilled water, potassium polysilicate solution, lithium polysilicate solution, and Ludox given. The resulting coating solutions had 10% total solids and had SiO.sub.2 :M.sub.2 O mole ratios, y, between 3.64 and 10 Analogous solutions containing 10% solids of the alkali metal polysilicates and no additional colloidal silica were prepared as comparative samples.

                                  TABLE 7__________________________________________________________________________Recipes for the Preparation of Lithium-Potassium CopolysilicateBarrier Coatings Having Various SiO.sub.2 :M.sub.2 O Mole Ratios,y and an Equimolar Ratio of Lithium to Potassium OxidesSi.sub.2 O:M.sub.2 OSource of      Mass of     Mass of                        Mass of                              Mass ofMole Colloidal      colloidal           Source of                  Potassium                        Inobond                               DistilledRatioSilica      Silica           Potassium                  Polysilicate                        Li 2043                              Water(y)  (Ludox       (g)  Polysilicate                  (g)   (g)   (g)__________________________________________________________________________3.64 None  --   K-4009 12.89 7.66  69.373.99 None  --   KASIL                   18.84 16.50 64.743.99 HS-40 1.73 K-4009 12.02 16.50 69.795.00 HS-40 5.60 K-409  10.00 13.68 70.635.00 AS-30 7.47 K-4009 10.00 13.70 68.805.00 CL-X  4.98 K-4009 10.01 13.73 71.307.00 HS-40 10.44           K-4009 7.52  10.34 71.757.00 AS-30 13.90           K-4009 7.49  10.28 68.227.00 CL-X  9.27 K-4009 7.52  10.31 72.9110.00HS-40 14.45           K-4009 5.45  7.50  72.64__________________________________________________________________________

B. Preparation of Coated Film Samples

Four inch circles were cut from biaxially oriented PET film (Hoechst Diafoil, Hostaphan the film was blown off with a jet of clean filtered air. The film samples were then plasma treated to improve wetting by barrier coating solutions and adhesion of dried barrier coatings. Plasma treatment was performed using a Plasma Preen microwave reactor operated at 50% power with 2 Torr of oxygen. The treatment duration was about 7 s.

Approximately 10 g of coating solution was dispensed onto the polymer film. A spreading spin cycle of 2 s at 350 rpm was followed by a spin cycle of 10 s at 2000 rpm. The coated films were dried in an oven maintained at 50

C. Oxygen Barrier Performance

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument. Samples were tested at 23 humidity. Table 8 presents oxygen transmission rates as a function of SiO.sub.2 :M.sub.2 O mole ratio, y, for a series of lithium-potassium copolysilicate barrier coatings with a lithium oxide mole fraction in (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y, x=0.5. As a point of reference, uncoated 0.5 mil thick PET film has an OTR of 115 cm.sup.3 /(m.sup.2 day atm) at 23 humidity. These results demonstrate that good barrier performance can be achieved in copolysilicate barrier coatings with SiO.sub.2 :M.sub.2 O mole ratios as high as 10. However, the range of SiO.sub.2 :M.sub.2 O mole ratios that yield satisfactory barrier performance depends on the identity of the colloidal silica source.

              TABLE 8______________________________________Oxygen Transmission Rates of Lithium-PotassiumCopolysilicate Barrier Coatings on 0.5 mil thickPET film vs. SiO.sub.2 :M.sub.2 O Ratio                          OTRSi.sub.2 O:M.sub.2 O    Source of Source of   (cm.sup.3 /[m.sup.2 day atm]Mole     Colloidal Potassium   at 23Ratio    Silica    Polysilicate                          relative humidity______________________________________3.64     None      K-4009      0.833.64     None      K-4009      0.283.99     None      KASIL                           0.343.99     None      KASIL                           0.173.99     HS-40     K-4009      0.523.99     HS-40     K-4009      0.395.00     HS-40     K-4009      0.355.00     HS-40     K-4009      0.335.00     AS-30     K-4009      1.065.00     AS-30     K-4009      0.235.00     CL-X      K-4009      0.235.00     CL-X      K-4009      0.297.00     HS-40     K-4009      0.937.00     HS-40     K-4009      0.487.00     AS-30     K-4009      0.657.00     AS-30     K-4009      0.557.00     CL-X      K-4009      11.807.00     CL-X      K-4009      12.8410.00    HS-40     K-4009      1.8910.00    HS-40     K-4009      1.40______________________________________
EXAMPLE 5 Simultaneous Variation of SIO.sub.2 :M.sub.2 O Mole Ratio, y, and Mole Fraction of Li.sub.2 O, x, in (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y Copolysilicate Coatings on Biaxially Oriented Pet Film

A. Preparation of Coating Solutions

A series of lithium-potassium copolysilicate barrier coating solutions were prepared according to the amounts listed in Table 9. With continuous stirring, distilled water, K-4009 potassium polysilicate solution, Inobond colloidal suspension of silicon dioxide containing 30% solids (DuPont Specialty Chemicals) were combined in the order given. The resulting coating solutions had 10% total solids and had SiO.sub.2 :M.sub.2 O mole ratios, y values of between 3.51 and 13. Analogous solutions containing 10% solids of the individual alkali metal polysilicates were prepared as comparative samples.

              TABLE 9______________________________________Recipes for the Preparation of Lithium-PotassiumCopolysilicate Barrier Coatings Having Various SiO.sub.2 :M.sub.2 OMole Ratios and Li.sub.2 O Mole Fractions                                      Mass ofMole    Si.sub.2 O:M.sub.2 O                       Mass of Mass of                                      Dis-Fraction        Mole     Mass of                       Inobond                                Ludox                                       tilledSolu-of Li.sub.2 O        Ratio    K-4009                       Li 2043 AS-30  Watertion x       y        (g)   (g)     (g)    (g)______________________________________1    0.00    4.05     42.94 0.00    9.63   147.432    0.00    7.67     26.12 0.00    1.97   141.913    0.00    15.0     14.57 0.00    47.31  138.124    0.33    4.05     30.57 20.95   6.85   141.625    0.50    9.5      11.46 15.71   37.05  135.796    0.50    9.5      11.46 15.71   37.05  135.797    0.50    15       7.53  10.32   47.21  134.958    0.67    4.05     16.40 44.96   3.68   134.979    1.00    4.05     0.00  72.73   0.00   127.2710   1.00    11.33    0.00  27.98   41.02  131.0011   1.00    15.0     0.00  21.35   47.09  131.55______________________________________

B. Preparation of Coated Film Samples

Four inch circles were cut from biaxially oriented PET film (Hoechst Diafoil, Hostaphan the film was blown off with a jet of clean, filtered air. The samples were then plasma treated with a Plasma Preen microwave reactor operated at 50% power and 2 Torr of oxygen. The treatment time was 5 s. Approximately 10 g of coating solution was dispensed onto the polymer film. A spreading spin cycle of 2 s at 50 rpm was followed by a spin cycle of 10 s at 2000 rpm. The coated films were dried in an oven maintained at 50 about 30 s. Several coated film samples were prepared with each coating solution described in Table 9.

C. Measurement of Oxygen Transmission Rates

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument. Table 10 presents the oxygen transmission rate results for biaxially oriented PET film (0.5 mil thick) coated with copolysilicate barrier layers having various SiO.sub.2 :M.sub.2 O mole ratios, y, and Li.sub.2 O mole fractions, x, in (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y as a function of relative humidity. As a point of reference, uncoated Hostaphan possesses an oxygen transmission rate of approximately 115 cm.sup.3 /[m.sup.2 day atm] when tested at 23

              TABLE 10______________________________________Oxygen Transmission Rates of Lithium-PotassiumCopolysilicate Barrier Coatings on 0.5 mil thickPET film vs. SiO.sub.2 :M.sub.2 O Ratio andMole Fraction of Li.sub.2 OSiO.sub.2 :M.sub.2 O    Mole Fraction                Relative  OTRMole Ratio    of Li.sub.2 O                Humidity  (cm.sup.3 /[m.sup.2 day atm]y        x           (%)       at 23______________________________________15.0     0.00        90        937.67     0.00        0         3011.3     1.00        90        6815.0     1.00        90        919.5      0.50        45        464.05     0.00        30        9.754.05     1.00        60        117.67     0.00        90        9815.0     0.00        0         1284.05     0.67        0         0.715.0     1.00        0         1254.05     0.33        90        804.05     0.67        90        2411.3     1.00        0         5615.0     0.50        45        1074.05     1.00        30        0.394.05     0.33        0         2.154.05     0.00        60        4.38______________________________________
EXAMPLE 6 Roll Coating of Lithium-Potassium Copolysilicate Barrier Coating Onto Biaxially Oriented Pet Film

A. Preparation of Coating Solutions

With continuous stirring, 4,513 g KASIL solution (PQ Corporation) having 8.30% w/w K.sub.2 O and 20.8% w/w SiO.sub.2 was mixed with 11,535 g distilled water. To the stirring potassium polysilicate solution was added 3,951 g Inobond lithium polysilicate solution. The resulting coating solution had a total solids level of 12%. The values of x and y in (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y were 0.5 and 4.0, respectively.

B. Preparation of Coated Films

Biaxially oriented PET film (Hoechst Diafoil, Hostaphan thick), was coated with the copolysilicate solution described above using roll coating at a speed of 200 fpm. Corona discharge treatment was used to increase the surface energy of the film surface immediately prior to application of the coating. Application of the coating was achieved with the use of a gravure cylinder in a reverse gravure configuration with a hard rubber backing roll. The ceramic-coated gravure cylinder possessed a laser engraved cell pattern with 220 lines per inch arranged at a 60 degree angle to the roll axis and a theoretical cell volume of 10 billion cubic microns per square inch.

C. Measurement of Oxygen Transmission Rate

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument. The average oxygen transmission rate obtained for 12 representative samples selected from the coated film was 0.77.+-38 cm.sup.3 /[m.sup.2 day atm] at 23 a point of reference, uncoated 0.5 mil Hostaphan possesses an oxygen transmission rate of approximately 115 cm.sup.3 /[m.sup.2 day atm] when tested at 23

EXAMPLE 7 Copolysilicate Coated Thick Pet Film

A. Preparation of Coating Solutions

A lithium-potassium copolysilicate barrier coating solution having values of x and y in (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y of 0.5 and 3.64, respectively, was prepared by adding, with continuous stirring, 176.8 g of Inobond of K-4009 potassium polysilicate to 694.2 g of distilled water.

B. Preparation of Coated Film Samples

Four inch circles were cut from biaxially oriented PET film (Hoechst Diafoil, Hostaphan scissors. Dust on the film was blown off with a jet of clean, filtered air. The film samples were then corona treated to improve wetting by barrier coating solutions and adhesion of dried barrier coatings. Corona treatment was performed using a Tantec Lab System II with hand-held ceramic roller electrode. The treatment duration was about 20 s. Spin coating of the films was accomplished by dispensing approximately 10 g of coating solution onto the polymer film. A spreading spin cycle of 2 s at 350 rpm was followed by a spin cycle of 10 s at 2000 rpm. The coated films were dried in an oven maintained at 50

C. Measurement of Oxygen Transmission Rate

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument. Samples were tested at 23 relative humidity. Table 11 presents oxygen transmission rate results for thick biaxially oriented poly(ethylene terephthalate) film (6.5 mil thick) uncoated or coated with copolysilicate barrier layers. Note that the OTR of uncoated PET film is inversely dependent on film thickness 8 cm.sup.3 /[m.sup.2 day atm] for 6.5 mil film vs. 115 cm.sup.3 /[m.sup.2 day atm] for 0.5 mil film at 23 contrast, the oxygen transmission rate of copolysilicate-coated biaxially oriented PET film is independent of substrate thickness. Thus the relative barrier improvement achievable for thick substrates is less than for thin substrates.

              TABLE 11______________________________________Oxygen Transmission Rates of Lithium-PotassiumCopolysilicate Barrier Coatings on 6.5 mil PET Film       Relative O.sub.2 Transmission Rate       Humidity (cm.sup.3 /[m.sup.2 day atm]Sample      (%)      at 23______________________________________Uncoated    0        7.25Uncoated    0        8.06Uncoated    0        7.72Average     0        7.68 .+-. 0.33Coated      0        0.54Coated      48       0.40Coated      48       0.22Average     48       0.31 .+-. 0.09______________________________________
EXAMPLE 8 Copolysilicate Barrier Coatings on Pet Bottles

This example demonstrates the oxygen barrier performance achieved by spray coating PET bottles with lithium-potassium copolysilicate barrier coatings. The main differences between coating PET film and bottles are (1) the greater thickness of bottle walls, typically 14 mil vs. the 0.5 mil or 6.5 mil film used in preceding examples, and (2) the process of spray coating. One skilled in the art of spray coating can achieve conditions that produce uniform barrier coating layers of appropriate thickness to achieve acceptable barrier performance.

A. Preparation of Coating Solutions

Two lithium-potassium copolysilicate barrier coating solutions having a values of x and y of 0.5 and 3.64 respectively, for (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y, were prepared for spray coating. The first coating solution, called Barrier 1 for this example, was prepared by adding, with continuous stirring, 70.7 g of Inobond 2043 lithium polysilicate and 51.56 g of K-4009 potassium polysilicate to 1,877 g of distilled water. The second coating solution, called Barrier 2 for this example, was prepared by adding 0.195 g of Genapol (Hoechst Celanese), an alkyl ethoxylate surfactant, to a 1003.35 g aliquot of Barrier 1. Each solution contained a total of 2.0% solids by weight. The solutions were thoroughly mixed immediately before spray coating.

B. Preparation of Coated Bottles

Twenty ounce injection stretch blow-molded PET bottles (Hoechst Celanese T-80 PET resin) were cleaned by wiping with acetone-soaked towlettes. Dried bottles were plasma treated to improve wetting by barrier coating solutions and adhesion of dried copolysilicate layers. Copolysilicate barrier solution was applied with a Badger air sprayer. Bottles were dried in an oven maintained at 80

C. Measurement of Oxygen Transmission Rates

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument with a package test module maintained at 30 relative humidity. Table 12 presents the oxygen transmission rate values for an oxygen partial pressure difference of 0.21 atm across the PET bottle wall, i.e. air on the outside, pure nitrogen on the inside. These data demonstrate an approximate two-fold decrease in oxygen transmission rate effected with a lithium-potassium copolysilicate barrier layer.

              TABLE 12______________________________________Oxygen Transmission Rates of Lithium-PotassiumCopolysilicate Barrier Coatings on PET Bottles              OTR (cm.sup.3 /[pkg day] at 30              0% Relative Humidity andSample ID Coating  21% O.sub.2 Atm.)______________________________________C1        None     0.082C2        None     0.081C3        None     0.078C4        None     0.073C5        None     0.077Average   None     0.078 .+-. 0.003F019704   Barrier 1              0.052F019706   Barrier 1              0.039F019707   Barrier 1              0.032F019708   Barrier 1              0.058F019709   Barrier 1              0.059F019711   Barrier 1              0.052Average   Barrier 1              0.049 .+-. 0.010F019716   Barrier 2              0.055F019717   Barrier 2              0.045F019718   Barrier 2              0.056F019720   Barrier 2              0.055F019721   Barrier 2              0.053Average   Barrier 2              0.053 .+-. 0.004______________________________________
EXAMPLE 9 Carbon Dioxide Barrier Performance of Copolysilicate Coated Biaxially Oriented Pet Films

Samples of the lithium:potassium copolysilicate coated biaxially oriented poly(ethylene terephthalate) film described in Example 6 were tested for carbon dioxide permeability. The average carbon dioxide transmission rate obtained for 4 representative samples selected from the coated film was 16.+-.11 cm.sup.3 /[m.sup.2 day atm] at 23 humidity. As a point of reference, uncoated 0.5 mil Hostaphan grade poly(ethylene terephthalate) film possesses a carbon dioxide transmission rate of approximately 440 cm.sup.3 /[m.sup.2 day atm] when tested at 23

EXAMPLE 10 Aroma Barrier Performance of Copolysilicate-Coated, Biaxially-Oriented Polypropylene Film

A. Preparation of Coating Solution

A lithium-potassium copolysilicate barrier coating solution having values of x and y of 0.5 and 3.64 for (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y, respectively, was prepared using Inobond lithium polysilicate, K-4009 potassium polysilicate, and water using the method described in Example 1. The resulting solution had a total solids level of 12% by weight.

B. Preparation of Coated Film Sample

Biaxially-oriented polypropylene film (Trespaphan thick) was corona treated, then primed with a poly(vinyl alcohol) solution by reverse gravure coating. The primed film was coated with the copolysilicate solution described in this example using roll coating at a speed of 200 fpm. Application of the coating was achieved with the use of a gravure cylinder in a reverse gravure configuration with a hard rubber backing roll. The ceramic-coated gravure cylinder possessed a laser-engraved cell pattern with 220 lines per inch arranged at a 60 of 10 billion cubic microns per square inch.

C. Measurement of Aroma Barrier

Aroma barrier performance was tested using cinnamaldehyde as a permeant. The cinnamaldehyde transmission rates of uncoated and copolysilicate-coated film (measured with liquid cinnamaldehyde in contact with the uncoated side of the film) are 0.095 g/(m.sup.2 day) and 0.022 g/(m.sup.2 day) at 23

EXAMPLE 11 Copolysilicate Coated Cycloolefinic Copolymer Film

A. Preparation of Solutions

A lithium-potassium copolysilicate barrier coating solution having values of x and y of 0. 5 and 3.64 respectively, for (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y, was prepared using Inobond lithium polysilicate, K-4009 potassium polysilicate, and water using the method described in Example 1. The resulting solution had a total solids level of 10% by weight.

B. Preparation of Coated Film

Four inch circles were cut from a corona-treated, biaxially oriented film of cycloolefinic copolymer, a copolymer of ethylene and norbornene, 0.8 mil thick, with a scalpel. Any dust on the film was blown off with a jet of clean, filtered air. Approximately 10 g of coating solution was dispensed onto the polymer film and subjected to a spin cycle of 10 s at 2000 rpm. The coated films were dried in an oven maintained at 50 C. for about 30 s.

C. Measurement of Oxygen Transmission Rate

Oxygen transmission rates were measured using a Mocon Oxtran 2000 instrument at 30 coated film exhibited an OTR of 28 cm.sup.3 /[m.sup.2 day atm] whereas an uncoated film exhibited an OTR of 2819 cm.sup.3 /[m.sup.2 day atm] under the same conditions.

Application of the method of this invention, and utilizing the improved coating compositions of the present invention result in a much less severe loss of barrier performance at high humidities than pure potassium polysilicates and develop haze at about half (when x0.5) the rate of pure lithium polysilicates. More specifically, the lithium-potassium copolysilicate coatings of the present invention reduce the rate of efflorescence of pure lithium polysilicates without sacrificing the barrier qualities of such lithium-polysilicate coatings. The present invention lithium-potassium polysilicate coatings provide superior barrier properties with reduced negative side-effects caused by efflorescence.

All references and patents cited above are incorporated herein by reference. Numerous modifications and variations of the present invention are included in the above-identified specification and are expected to be obvious to one of skill in the art. Such modifications and alterations to the compositions and processes of the present invention are believed to be encompassed in the scope of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the hazing rate (in absolute percentage per day, i.e., a value of one indicates an increase of, for example, from 5% to 6% haze in a single day) vs. the mole fraction x of Li.sub.2 O in the copolysilicate (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y. This figure depicts the dependence of the hazing rate on the amount of lithium in the coating composition.

FIELD OF THE INVENTION

The present invention relates generally to silicate-based barrier coatings for polymeric articles.

BACKGROUND OF THE INVENTION

Alkali metal polysilicates have long been known as protective coatings that modify the permeability or surface characteristics of polymeric films and other articles. Lithium (Li), sodium (Na), and potassium (K) polysilicates are known to be effective as protective coatings for a variety of surfaces. For example, Japanese Patent Publication No. H7-18202, published Jan. 20, 1995 refers to a water-insoluble, coating material and binder for use on metals, synthetic resins, glass, wood, cement, etc, which contains mixtures of an aqueous solution of sodium or potassium silicate and an aqueous solution of lithium silicate, where the ratio of the sodium or potassium silicate to lithium silicate is in the range of 1-3.

As another example, Hecht and Iler, Canadian Patent No. 993,738, describe a gas and liquid-impermeable coating for polymeric substrates comprising lithium polysilicate having a mole ratio of SiO.sub.2 to Li.sub.2 O of about 1.6 to 4.6. However, polymeric articles are known to become hazy after certain polysilicate coatings have been incorporated. The tendency of sodium (Na) polysilicate coatings to effloresce, i.e., to become covered by powdery crystalline material as a result of atmospheric exposure, has been documented [Weldes and Lange, Ind. Eng. Chem., 61(4):28-44 (1969)]. This characteristic has similarly been observed for lithium polysilicate coatings by the present inventors. In contrast, pure potassium polysilicate coatings do not effloresce, but suffer severe loss of barrier performance above 50% relative humidity. Pure lithium polysilicate coatings, on the other hand, exhibit little or no loss of barrier performance over the same relative humidity range.

There remains a need in the art of barrier coatings for coating compositions and methods which overcome the above deficiencies, and are widely available as vapor, gas and/or aroma barriers for polymeric articles, e.g., packaging products.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a method for providing improved vapor, gas and aroma barrier properties at high relative humidities to a polymeric substrate. The method involves coating the substrate with a barrier coating solution containing a lithium-potassium copolysilicate of the formula (Li.sub.2 O).sub.x (K.sub.2 O).sub.1-x (SiO.sub.2).sub.y wherein x is the mole fraction of Li.sub.2 O in the combined alkali metal oxides (M.sub.2 O), and y is the SiO.sub.2 :M.sub.2 O mole ratio. In this method, x ranges from 0 to 1, inclusive. Specifically, if x is less than 1, y is between 1 and 10; and if x is 1, y is greater than 4.6.

In another aspect, the present invention provides a novel vapor, gas and/or aroma barrier coating solution for polymeric articles comprising a copolysilicate of the above formula, which overcomes deficiencies in the art. The aforementioned coating solution is represented by the general formula above, except that y is greater than 4.6 if x is less than 1, and x is greater than 0.5, if y is between 1 and 10. The coating solution is preferably colorless or transparent and can contain a suitable surfactant.

Another aspect of this invention provides a polymeric article coated with the above described barrier coating solution. The article may be typically a polymer film or membrane, such as those employed in the packaging of foodstuffs, a sheet, or a rigid or semi-rigid container, e.g., a bottle.

Other aspects and advantages of the present invention are described in the detailed description below and in the claims.

CROSS-REFERENCE TO OTHER APPLICATIONS

This is a divisional of pending U.S. patent application Ser. No. 08/857,923, filed May 16, 1997, now U.S. Pat. No. 5,882,798, which is a continuation-in-part of U.S. patent application Ser. No. 08/652,287, filed May 22, 1996, now abandoned.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1949914 *2 Jan 19326 Mar 1934Grasselli Chemical CoWater-resistant alkaline silicate compositions
US2998328 *22 Jul 195729 Aug 1961Amercoat CorpProtective coating and method of producing same
US3102038 *22 Oct 195927 Aug 1963Ind Metal Protectives IncProtective coating
US3130061 *6 Feb 196121 Apr 1964American Pipe & Constr CoInorganic coating composition
US3180747 *3 Aug 196127 Apr 1965Exxon Research Engineering CoProtective coating
US3282729 *27 Feb 19631 Nov 1966Union Carbide CorpBarrier coated thermoplastic olefin polymer substrates
US3492137 *20 Sep 196827 Jan 1970Du PontSiliceous compositions
US3522066 *6 Dec 196628 Jul 1970Lithium CorpProcess for preparing aqueous mixed lithium and sodium (and/or potassium) silicate solutions
US3533816 *22 Oct 196513 Oct 1970Du PontPreparation of high ratio alkali metal silicates
US3706603 *12 Apr 197119 Dec 1972Albright & WilsonMetal coatings comprising hexavalent chromium,trivalent chromium,silica or a silicate and an alkali metal cation
US3884863 *29 Dec 197220 May 1975Exxon Research Engineering CoZinc enriched lithium silicate-latex coating composition
US4101050 *14 Sep 197618 Jul 1978Polysar LimitedFilled-polystyrene laminates
US4247576 *9 Mar 197927 Jan 1981Hercules IncorporatedProcess for preparing silicate coated polypropylene film
US4466831 *27 Sep 198221 Aug 1984Halliburton CompanyRapidly dissolvable silicates and methods of using the same
US4466832 *29 Sep 198221 Aug 1984Daikin Kogyo Company, LimitedComposition for forming hydrophilic coating
US4503158 *13 Apr 19835 Mar 1985Rhone-Poulenc IndustriesDouble or mixed silicates of alkali metal and other glass modifier metal(s) used to prepare glass compositions
US4537866 *29 Mar 198427 Aug 1985Uop Inc.Method of preparing silicate composition
US4681818 *18 Mar 198621 Jul 1987The United States Of America As Represented By The Administrator Of The National Aeronautics And Space AdministrationOxygen diffusion barrier coating
US4945074 *1 May 198931 Jul 1990Blount David HPolymeric alkali metal silicate glass
US5049609 *13 Mar 199017 Sep 1991The Goodyear Tire & Rubber CompanyCoating composition and coated tire
US5055137 *11 Dec 19898 Oct 1991Zyp Coatings, Inc.Water-insoluble high temperature ink
US5130110 *18 Dec 199014 Jul 1992Societe Francaise HoechstProcess for obtaining refractory metal oxides based on silica by sol-gel route in aqueous medium
US5164003 *28 Mar 199017 Nov 1992Ceram Tech International, Ltd.Room temperature curable surface coating and methods of producing and applying same
US5183704 *11 Feb 19912 Feb 1993Armstrong World Industries, Inc.Highly microporous 2:1 layered silicate materials
US5238668 *14 Nov 199024 Aug 1993Henkel Kommanditgesellschaft Auf AktienProcess for production of potassium silicate solutions by the addition of tempered quartz to hydrothermally reacted quartz and koh, and hydrothermal reaction thereof
US5244729 *31 Jan 199214 Sep 1993Imperial Chemical Industries PlcPolymeric film comprising a coating layer of vermiculite platelets
US5344633 *14 Jun 19936 Sep 1994Eka Nobel AbAlkali metal silicate composition with potassium compound additive
US5354548 *2 Nov 199211 Oct 1994Unilever Patent Holdings B.V.Porous three-dimensional inorganic oxide structure with myriad cavities interconnected by holes
US5462779 *2 Mar 199331 Oct 1995Consorzio Ce.Te.V. Centro Tecnologie Del VuotoThin film multilayer structure as permeation barrier on plastic film
US5503820 *28 Nov 19942 Apr 1996E. I. Du Pont De Nemours And CompanyMethod for preparing low-concentration polysilicate microgels
US5560773 *13 Jun 19951 Oct 1996Fmc CorporationPenetrating sealant composition
US5565273 *5 Aug 199315 Oct 1996Vetrotech AgTransparent heat protection element
US5575953 *4 Apr 199519 Nov 1996Hitachi Powdered Metals Co., Ltd.Coating compositions for the inner wall of cathode-ray tube
US5853830 *6 Jun 199729 Dec 1998Hoechst Trespaphan GmbhTransparent barrier coatings exhibiting reduced thin film interference
CA993738A1 *8 Jun 197327 Jul 1976Du PontSilicate coated polymeric shaped objects
EP0518646A1 *10 Jun 199216 Dec 1992Imperial Chemical Industries PlcPolymeric film
EP0518647A1 *10 Jun 199216 Dec 1992Imperial Chemical Industries PlcPolymeric film
GB1007482A * Title not available
GB1424425A * Title not available
GB1532847A * Title not available
JPH0718202A * Title not available
Non-Patent Citations
Reference
1 *Database WPI Section CH, Week 9439, Derwent Publications Ltd., London, GB; Class A26, AN 94 313903 XP002040546 & JP 06 240 174 A (Asahi Kagaku Kohyo KK) Aug. 30, 1994.
2Database WPI Section CH, Week 9439, Derwent Publications Ltd., London, GB; Class A26, AN 94-313903 XP002040546 & JP 06 240 174 A (Asahi Kagaku Kohyo KK) Aug. 30, 1994.
3H. H. Weldes & K.R. Lange, "Properties of Soluble Silicates", Indus. Engin. Chem., 61(4):29-44 (Apr. 1969).
4 *H. H. Weldes & K.R. Lange, Properties of Soluble Silicates , Indus. Engin. Chem. , 61(4):29 44 (Apr. 1969).
5H. van Olphen, "Clay Minerology", An Intro. To Clay Colloid Chemistry, 27:69-71 (1963).
6 *H. van Olphen, Clay Minerology , An Intro. To Clay Colloid Chemistry , 27:69 71 (1963).
7N. R. Horikawa et al, "Drying and Water Resistance of Silicate Films", Adhesives Age,10(7):30-34 (1967).
8 *N. R. Horikawa et al, Drying and Water Resistance of Silicate Films , Adhesives Age ,10(7):30 34 (1967).
9 *Patent Abstracts of Japan, vol. 095, No. 004, May 31, 1995 & JP 07 018202 A Agency of Ind. Science & Technol., Jan. 20, 1995.
10W. J. Ward et al, "Gas Barrier Improvement Using Vermiculite & Mica in Polymer Film", J. Membrane Sci., 55:173-180 (1991).
11 *W. J. Ward et al, Gas Barrier Improvement Using Vermiculite & Mica in Polymer Film , J. Membrane Sci. , 55:173 180 (1991).
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US62549946 Jun 19973 Jul 2001Hoechst Trespaphan GmbhMethod of priming polyolefin articles for coating
US636867715 May 20019 Apr 2002Hoechst Trespaphan GmbhMethod of priming polyolefin articles for coating
US6599622 *3 Oct 200029 Jul 2003Exxonmobil Oil CorporationCoated films with improved barrier properties
US663862819 Apr 200228 Oct 2003Ronald R. SavinSilicate coating compositions
US711879016 Sep 200310 Oct 2006Hoechst TrespaphanProcess for producing coated polymeric articles and the articles produced thereby
US808029730 Apr 200720 Dec 2011Nanopack, Inc.Barrier coatings for films and structures
Classifications
U.S. Classification428/446, 428/523, 428/521, 428/480, 428/475.5
International ClassificationC08J7/04, C09D1/02, C08J7/06
Cooperative ClassificationC09D1/02, C08J7/045, C08J7/06
European ClassificationC08J7/04D1, C09D1/02, C08J7/06
Legal Events
DateCodeEventDescription
24 Jul 2012FPExpired due to failure to pay maintenance fee
Effective date: 20120606
6 Jun 2012LAPSLapse for failure to pay maintenance fees
16 Jan 2012REMIMaintenance fee reminder mailed
23 Nov 2007FPAYFee payment
Year of fee payment: 8
2 Dec 2003FPAYFee payment
Year of fee payment: 4
27 Oct 1999ASAssignment
Owner name: HOECHST TRESPAPHAN GMBH, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:BATTITO, FRANK P.;REEL/FRAME:010334/0769
Effective date: 19991020
Owner name: HOECHST TRESPAPHAN GMBH BERGSTRASSE NEUNKIRCHEN GE
21 Oct 1999ASAssignment
Owner name: HOECHST TRESPAPHAN GMBH, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HUBBARD, MICHAEL A.;MCCAULLEY, JAMES A.;HOLCOMB, DOUGLASR.;REEL/FRAME:010339/0615;SIGNING DATES FROM 19990929 TO 19991007
Owner name: HOECHST TRESPAPHAN GMBH BERGSTRASSE NEUNKIRCHEN GE
13 Sep 1999ASAssignment
Owner name: HOECHST CELANESE CORPORATION, NEW JERSEY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HUBBARD, MICHAEL A.;MCCAULLEY, JAMES A.;BATTITO, FRANK P.;AND OTHERS;REEL/FRAME:010230/0995
Effective date: 19970515
Owner name: HOECHST TRESPAPHAN GMBH, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HOECHST CELANESE CORPORATION;REEL/FRAME:010230/0491
Effective date: 19971230